a good start would be to get kdevelop and start a new project.. there should be a template for just about anything in kde you want to make. i have worked with kicker applets a little.. i have only used c++ for them, but id bet there are ways to use ruby and python like reddazz mentioned..
in addition to using a template from kdevelop you can look at the source for kde, and check out the applets that come with kde.. they are in the kdebase package under kicker/applets/ ..
good luck
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